Hand gesture control system

ABSTRACT

A system is provided for rapidly recognizing hand gestures for the control of computer graphics, in which image moment calculations are utilized to determine an overall equivalent rectangle corresponding to hand position, orientation and size, with size in one embodiment correlating to the width of the hand. In a further embodiment, a hole generated through the utilization of the touching of the forefinger with the thumb provides a special trigger gesture recognized through the corresponding hole in the binary representation of the hand. In a further embodiment, image moments of images of other objects are detected for controlling or directing onscreen images.

FIELD OF INVENTION

This invention relates to computer graphics and, more particularly, to ahand recognition computer control system.

BACKGROUND OF THE INVENTION

It will be appreciated that the control of onscreen images in a computerenvironment is desirable in order to provide realtime interaction. Oneof the more difficult problems associated with the direction ofcharacter movement is when one seeks to optically detect hand gesturesin real time. The time necessary to acquire or recognize the handgesture, both in a cluttered environment and against a naturalbackground, can exceed several seconds, a relatively long time forinteractive applications.

During optical recognition of the hand gesture, it is oftentimesnecessary to compare the digital images of the hand with a template sothat a match can be made between the predetermined template and the handgesture. In so doing, many multiplications must be performed resultingin a relatively large lag time for hand gesture recognition.

One such hand gesture recognition system is described in U.S. patentapplication Ser. No. 08/391,955 now U.S. Pat. No. 5,594,469 by WilliamT.

Freeman and Craig D. Weissman, filed on Feb. 25, 1995 incorporatedherein by reference. While the system described therein operatessatisfactorily to uniquely determine particular hand gestures, there isnonetheless a need for a more simplified system which operates morequickly and accurately to detect hand gestures.

It is also a requirement, especially in the games industry, for anexceptionally inexpensive method for hand gesture recognition.

SUMMARY OF THE INVENTION

In order to accomplish hand gesture control in an efficient, timesaving, and inexpensive manner, in the Subject System the hand ischaracterized by image moments which refer in the subject case tospatially weighted averages of image intensities. From these imagemoments can be found a corresponding rectangle which has the same set ofimage moments. The hand gesture is characterized through theorientation, position, length and width of the corresponding rectangle.This provides an exceptionally fast recognition system for a largevariety of hand gestures without having to resort to complicated imageprocessing.

For instance, for graphical object control in which onscreen charactersare to be controlled by a participant or user, it is desirable toeliminate the necessity for a mouse or a joystick in favor a readilyavailable item, namely one hand. The ability to be able to sense handgestures for the control of the game eliminates the requirement forcostly input apparatus. More importantly, with a joystick there are onlytwo degrees of freedom which can be controlled; but with the hand thereare multiple types of actions that can be expressed through articulationof the hand. As a result, multiple parameters such as orientation,horizontal and vertical position, and projected length and width can besensed.

In order to provide game control or other onscreen graphical objectcontrol, in one embodiment hand gestures are sensed optically throughthe utilization of a camera with the image being converted into adigital representation such that the position of the image of the hand,its length and width, and its orientation are detected. This providesfive different measurements of the hand gesture, namely horizontal andvertical position, projected length and width and orientation. Ratherthan sensing the exact 3-d configuration of the hand, it is a finding ofthis invention that computer control can be robustly provided throughthe above criteria.

In particular, the X projection and Y projection of the image arecalculated along with the diagonal projection followed by the generationof image moments through a specialized calculation so as to derive arectangle having a given position, length and width, and orientation,with the characteristics of the rectangle then providing a robustsimplified means of detecting a particular hand gesture.

In one embodiment, a specialized trigger gesture, which is easilyrecognized, involves the providing of a circle with the thumb and theforefinger to provide a hole. This type of gesture is very easilyrecognized by the subject system and provides the system with a signalindicating that the user has initiated the trigger gesture.

This same hand gesture can be utilized to provide a trigger for anyaction which the computer is to execute, including, for instance, thefiring of a gun, the initiation of a rocket blast off sequence, or infact any other machine action.

In a further embodiment, not only are hand gestures easily detectedthrough the utilization of the image moment calculation, additionally,body movement can be detected through the detection of the moments ofthe image and analysis of the five measurements derived from theequivalent rectangle. Noting that the center of the rectangle is thecenter of mass of the object, one can detect the center of mass andtherefore its movement. In this instance, one is looking at only onecomponent of the rectangle to provide onscreen motions of a character.

More particularly, simple position and size measurements of an objectcan be calculated by measuring image moments. This assumes that theobject of interest, normally the hand, dominates the image and that thebackground is uniform or can be subtracted out. The following equationsdetail the weighted average that is utilized to calculate image moments.If I (x, y) is the image intensity at position x, y, then the imagemoments up to second order are: ##EQU1##

We can find the position, x_(c), y_(c), orientation θ, and width l₂ andlength l₁, of an equivalent rectangle which has the same moments asthose measured in the image [1]. Those values give a measure of thehand's position, orientation, length and width. We have: ##EQU2##

Note that in Equations 1-5, the measurements corresponding to theseequations are based on summations over the entire image, so that theywill be robust against small changes in the image. The five abstractedparameters are independent of the overall contrast of the hand againstthe background. The calculation of Equations 2-5 are done just once perimage, not once per pixel. The integrals of Equation 1 require fivemultiplies and six additions per pixel, the quadratic factors in x and ybeing precomputed.

Note, with respect to a camera field of view including one's arm becauseone edge of an arm will always be off the edge of the picture, thelength of the hand, L₁, is then coupled to the Y_(c) position. Thus, theinformation provided by L₁ is redundant with the information provided byY_(c). Thus, one can use the L₂ measurement for such camera field ofview, but not the L₁.

While the above has been described in terms of a generalized processor,an artificial retina chip such as described in K. Kyuma, E. Lange, J.Ohta, A. Hermanns, B. Banish, and M. Oita, Nature, Volume 372, Number197, 1994 can be used to generate some image projections as opposed tocalculating them with a general processor. These image projections canthen be utilized by a microprocessor to calculate the image moments.When the artificial retina chip is coupled to a microprocessor, thisprovides for fast calculation of the image moments. Thus, by utilizingthe two projections of the image as available from an artificial retinachip, one can calculate image moments without having to resort to theutilization of the double sums of the previous equations or resorting tomicroprocessor calculation of all three image projections. As a result,Equations 6-9 presented hereinafter show how 1-d integrals can beutilized in the computation of the image moments.

Let the vertical, horizontal, and diagonal projections be: ##EQU3## and

Then the image moments can be computed from those projections by [1]:##EQU4##

These single sums will be faster to compute than double sums of Eq. (1).

The result is that hand gesture recognition or indeed body positionrecognition can be accomplished in milliseconds as opposed to severalseconds.

In summary, a system is provided for rapidly recognizing hand gesturesfor the control of computer graphics, in which image moment calculationsare utilized to determine an overall equivalent rectangle correspondingto hand position, orientation and approximate shape, with shape in oneembodiment correlating to the length and width of the hand. In a furtherembodiment, a hole generated through the utilization of the touching ofthe forefinger with the thumb provides a special trigger gesturerecognized through the corresponding hole in the binary representationof the hand. In a further embodiment, image moments are utilized todetermine the center of mass of an image for controlling or directingonscreen images.

BRIEF DESCRIPTION OF THE DRAWING

These and other features of the Subject Invention will be betterunderstood taken in conjunction with the Detailed Description inconjunction with the Drawing of which:

FIG. 1 is a block diagram of an artificial retina chip embodiment of thesubject invention in which hand gestures are detected and decoded forgame control;

FIG. 2 is a flow chart illustrating the process of detecting handgestures and providing game control signals for graphics generation;

FIGS. 3A-3E are photographs of the digitized pictures of selected handgestures and rectangles corresponding to the gestures;

FIGS. 4A, 4B, and 4C are respective pictures of the digital image ofselected hand gestures and the control of an onscreen graphical object,in this case a car, with the orientation of the car controlled by theorientation of the hand and the speed of the car controlled by the widthof the hand;

FIG. 5 is a block diagram illustrating the detection of a specialtrigger gesture in the form of a hole for game control;

FIG. 6 is a series of photographs of the digital image of a handgenerating the special hole trigger gesture, including the correspondingrectangle, with the detection of the trigger gesture indicated by achange in the fill pattern of the rectangle;

FIG. 7 is a diagrammatic representation of the image projections for adigital image of a hand, indicating by the circled text whether thatprojection can be calculated by the artificial retina chip (AR) or themicroprocessor (uP); and,

FIGS. 8A-8E are a series of pictures and diagrams indicating the imageof a human being as detected by an artificial retina chip, itscorresponding rectangle, and the corresponding action that an onscreenimage of the individual's foot is to represent upon detection of aparticular characteristic of the detected image, namely, "center ofmass" location.

DETAILED DESCRIPTION

Referring now to FIG. 1, in one embodiment, hand gesture recognitionincludes a system for scanning an area including a camera having a lens10, an artificial retina chip 12, and a microprocessor 14 which isutilized to process the images to provide for the aforementioned imagemoment detection and control signals which are in turn applied to a gamecontrol unit 16 for driving a graphics generation unit 18 that providesthe appropriate graphics on display 20.

As mentioned hereinbefore, it is the purpose of the subject invention torapidly determine characteristics of a hand or other object in the fieldof view of lens 10 so as to be able to provide for the requisite gamecontrol, or in fact, any type of computer control display.

More particularly, and referring now to FIG. 2, that which is the outputof microprocessor 14 is the position; orientation and dimensions of theequivalent rectangle. In order to provide for this output, as can beseen at 22, in one embodiment, artificial retina chip 12 calculates thex projection. The y projection of the image is calculated at 24. Thesetwo calculations can either be done separately or in the illustratedembodiment performed by processors carried by the artificial retinachip.

While these two projections are necessary for the calculation of imagemoments, microprocessor 14 is utilized to calculate the diagonalprojection as illustrated at 26 so as to complete an image momentcalculation at 28 in accordance with Equations 6 through 9. After havingcalculated image moments, the rectangle corresponding to these imagemoments is calculated at 30 such that the resulting rectangle, analyzedas to orientation, position, length and width, provides requisitesignals for game control unit 16 to be able to drive the appropriategraphics generation unit 18 so as to provide the requisite on-screendisplay. It will be appreciated that the calculation of the rectangle asillustrated at 30 is accomplished by Equations 2-5.

What is therefore accomplished through the utilization of an artificialretina chip is a rapid means of calculating image moments throughprecalculation of x and y projections by the artificial retina chip,followed by a calculation of the diagonal projection in themicroprocessor. It will be appreciated that the calculation of thediagonal projection is accomplished in accordance with Equation 8.

It will be appreciated that what is meant by an x projection and a yprojection is merely the sum of all of the image intensities in the xdirection and the y direction respectively. For instance, for the xprojection, one merely adds up all of the pixels in every column,yielding one sum for every column. The same is done for every row suchthat with its orthogonal representation, the sums of image intensitiesmay be utilized in the derivation of the corresponding rectangle. Itwill be appreciated that the sums along each of the orthogonal axes,plus the diagonal axis is used by Equation 9 to calculate the imagemoments.

Referring now to FIGS. 3A-3E, the resulting rectangles for thecorresponding images are shown. For instance, in FIG. 3A, the image asshown at 40 is a side view of a hand at a given orientation asillustrated by a center line 42. It will be appreciated that theresulting rectangle 44 is oriented along the same center line, but has awidth 46 corresponding to the width of the hand, and a length 48corresponding to the length of the hand.

As can be seen, while images in themselves are rather complicated innature, they can be characterized in a simple way through the rough sizeand shape of a corresponding rectangle. As can be seen in FIG. 3B, aside view of hand 50, having a center line 52 is characterized byrectangle 54, having center line 52, a length 56 and width 58. The imageof a flat hand illustrated at FIG. 3C at 60, is characterized by acorresponding rectangle at 62 whereas a thumbing gesture, as illustratedby image 64, is characterized by a corresponding rectangle 66. Referringto FIG. 3E, the image of FIG. 3D is shifted to the right as illustrated68, with a corresponding change in the position and orientation of thecorresponding rectangle 70 being depicted.

Having described a relatively simple way of rapidly detecting handgestures, it will be appreciated, as illustrated in FIGS. 4A, 4B, and4C, that different hand gestures can be utilized to create differentpositions and motions of an on-screen image. For instance, thedownwardly projecting hand 80 causes the car 82 to be oriented in adirection corresponding to hand 80, whereas hand position 84 causes car82 to move in the direction indicated by the hand. However, a flat hand86 causes car 82 to speed up in accordance with the width of the hand.What will be appreciated is not only can the direction of on-screenimages be changed in accordance with hand gesture control, othercharacteristics of the image such as its velocity can also be changedthrough hand gesture detection.

Referring to FIG. 5, as part of hand gesture recognition in accordancewith the subject invention, it is possible to detect a unique triggergesture, which is then utilized to enter into a programming sequence orto provide some other computer control regime. In this case, an image isdetected at 90, is binarized at 92, with holes in the binarized imagebeing counted at 94 by a method such as described in [1] such that forgame control, the number of holes is utilized via a control unit 96 tocontrol screen display 98. The holes in this case are those generatedthrough the touching of thumb with the index finger to form a circle.This is a highly recognizable image. In one embodiment, the triggergesture can be used to control the shading of a particular rectangle.For instance, as illustrated in FIG. 6, with the thumb and theforefinger not touching, the equivalent rectangle 100 is portrayed asbeing opaque. Rather, when the trigger gesture is completed by thetouching of the thumb with the forefinger as illustrated at 104, theresulting rectangle 106 may be shaded or colored differently. Thedifference in shading of the rectangles indicates the detection of thiseasily recognized trigger gesture.

Referring now to FIG. 7, given an image at 110 of a hand, the horizontalimage projection, the vertical image projection, and the diagonal imageprojection are as illustrated respectively by curves 112, 114, and 116.The processing in order to generate these curves is, as mentionedbefore, in the artificial retina chip for both the horizontal andvertical projections, with the processing being in the microprocessorfor the diagonal projection.

As mentioned hereinbefore, and referring now to FIGS. 8A-8E, it ispossible for the subject system to recognize images other than hand.What will be seen from FIGS. 8A-8E is that a camera including lens 10and artificial retina chip 12, is viewing a scene 200 in which anindividual posed so as to present different aspects of the individual'sbody as shown by image 202. In a skate boarding situation, theindividual shifts his weight to his right on a board in accordance withhis body position as illustrated in FIG. 8A. The corresponding positionof the individual is illustrated by rectangle 204. As illustrated to theright of this rectangle is a side view of the individual's leg 208 onskateboard 210, with the skateboard moving to the left (the individual'sright) as illustrated by arrow 211.

Alternatively, as illustrated in FIG. 8B by the individual's position inimage 212, the corresponding rectangle 214 indicates that the individualis standing straight up on the skateboard, with the individual's leg 208as illustrated, such that the board moves straight in the direction 216.

As illustrated by image 220, the individual seeks to have his skateboardmoved to his left by leaning to the left. This is indicated by thecorresponding rectangle 222, in which the leg 208, as illustrated inFIG. 8C, leans to the individual's left (on-screen right) with theskateboard going on-screen right as illustrated at 224.

As illustrated by image 230, it is oftentimes desirable to hop theskateboard by jumping vertically. This is indicated the correspondingrectangle 232, which causes the on-screen image of the skateboard, alongwith the individual here illustrated at 240, to execute a jumpingmaneuver.

It will be appreciated that in FIGS. 8A, 8B, and 8C the position of therectangle, x_(c) and y_(c) of equation 2, the so-called "center of mass"of the rectangle, is within a given distance from the center of crosshairs 242 and 244. However, when this center of mass rises vertically asillustrated by rectangle 232 outside a predetermined threshold distanceestablished by the system, the subject system recognizes this positionof the rectangle as being one indicating a jump. Thus, when the centerof mass of rectangle 232 exceeds a predetermined vertical thresholddistance from the cross hairs, the jump sequence is executed on-screen.

As can be seen by image 250, the individual is in a crouch position.This crouch position is reflected by the center of mass of rectangle 252being below the intersection of the cross hairs by an amount whichexceeds a predetermined threshold. This being the case, the imageportrayed on-screen is that as illustrated at 254 to be a skateboardingindividual 256 dipping down under a bridge-like structure 258.

What will appreciated is that the so-called "center of mass" of arectangle, can be determined by Equation 2. This center of mass is thenutilized to determine the motion of the on-screen image or, in fact,which on-screen image will be presented.

By center of mass of an image is meant the position in the image thatwould be the center of mass of an object which had a local mass densityproportional to the image intensity at each pixel. The program forgenerating image moments and on-screen image control is now presented.

Having now described a few embodiments of the invention, and somemodifications and variations thereto, it should be apparent to thoseskilled in the art that the foregoing is merely illustrative and notlimiting, having been presented by the way of example only. Numerousmodifications and other embodiments are within the scope of one ofordinary skill in the art and are contemplated as falling within thescope of the invention as limited only by the appended claims andequivalents thereto.

I claim:
 1. A system for rapidly recognizing non-regular objects inspace for the control of computer graphics, comprising:means forscanning an area at which said object is expected to exist and forgenerating an electronic image in the form of a pixel representation ofsaid object; means for detecting and calculating image moments frompixel intensities of pixels in said pixel representation; means fordetermining, based upon the calculated image moments, an overallrectangle equivalent to the object and having a position, orientation,length and width corresponding to object position, orientation, lengthand width; and, means for identifying parameters of said rectangle andgenerating a corresponding control signal.
 2. A system for rapidlyrecognizing hand gestures for the control computer graphics,comprising:means for scanning an area at which a hand is expected toexist and for generating an electronic image in the form of a pixelrepresentation of said hand; means for calculating image moments frompixel intensities of pixels in said pixel representation; means fordetermining, based upon the calculated image moments, an overallrectangle equivalent to the hand and having a position, orientation,length and width corresponding to a position, orientation, length andwidth of the hand; and, means for correlating said rectangle with apredetermined hand gesture and for providing a signal representing theresult of said correlation.
 3. The system of claim 2 wherein thecorrelating means responds to at least one of the position, theorientation, the length and the width of the rectangle exceeding apredetermined threshold by generating the control signal to control saidcomputer graphics in a predetermined manner.
 4. The system of claim 2,wherein said size corresponds to the width of the hand making said handgesture.
 5. The system of claim 2, wherein said correlating meansresponds to the existence of a hole within a region of said pixelsgenerated through touching of a finger and a thumb of said hand byproviding a predetermined signal upon correlating the correspondingrectangle to that hand gesture.
 6. The system of claim 5 furthercomprising means for determining that the hole exist by counting anumber of holes in said pixel representation.
 7. A system for rapidlyrecognizing a non-regular image, comprising:means for generating arepresentation of said image; means for detecting and calculating imagemoments from pixel intensities of pixels in said pixel representation;means for determining, based on the calculated image moments, an overallgeometric structure equivalent to the image and having length, width andheight characteristics corresponding to parameters of said image; and,means for correlating said structure with a predetermined structure andfor providing a signal representing the result of said correlating. 8.The system of claim 7 wherein the correlating means responds to at leastone of the length, the width and the height characteristics of thestructure exceeding a predetermined threshold by providing the signal tocontrol computer graphics in a particular manner.
 9. The system of claim7, wherein said image is that of a hand, wherein said pixel generatingmeans includes means for generating an electronic binary pixel imagecorresponding to said hand; and further comprising;means for determininga change in image topology corresponding to the exact time a portion ofsaid image is in the form of a completed circle corresponding to thattime at which a hole generated through touching of a finger of with athumb of the hand is completed; and means for providing a predeterminedsignal upon detection of said completed circle, whereby said completedcircle can be used as a staccato button-like-push to effectuate a handgenerated on/off control action.
 10. The system of claim 9 wherein saidpredetermined signal is a trigger signal.
 11. The system of claim 10,wherein said trigger signal is generated in response to the detection ofa hole within a region of said generated pixels.
 12. The system of claim11, wherein said hole is detected by counting the number of holes insaid binary pixel image.
 13. A method of controlling a digitalrepresentation, comprising the steps of:imaging an object to generateobject images; determining a movement of the object based upon at leastone of an orientation and a position of a first geometric configurationhaving a contour different than a contour of the object andcorresponding to image intensities of a first of the object images andat least one of an orientation and a position of a second geometricconfiguration having a contour different than a contour of the objectand corresponding to image intensities of a second of the object images;and controlling a digital representation based upon the determinedmovement.
 14. The method of claim 13, further comprising the stepsof:computing a first spatially weighted average intensity of thegenerated first image in its entirety; computing a second spatiallyweighted average intensity of the generated second image in itsentirety; generating the first geometric configuration based upon thecomputed first spatially weighted average; and generating the secondgeometric configuration based upon the computed second spatiallyweighted average.
 15. The method of claim 13, wherein:the imaged objectis a hand; the geometric configuration is a rectangle; and the movementcorresponds to a gesture.
 16. The method of claim 15, wherein:thegesture is a circle formed with a thumb and a finger of the hand; andthe digital representation is controlled such that an action istriggered responsive to the thumb contacting the finger to form thecircle.
 17. The method of claim 13, further comprising the stepsof:computing a first spatially weighted average intensity of thegenerated first image; computing a second spatially weighted averageintensity of the generated second image; generating the first geometricconfiguration based upon the computed first spatially weighted averageintensity, wherein the center of mass of the object in the first imagecorresponds to the center of the first geometric configuration; andgenerating the second geometric configuration based upon the computedsecond spatially weighted average intensity, wherein the center of massof the object in the second image corresponds to the center of thesecond geometric configuration; wherein the orientation and the positionof the second geometric configuration is determined based on adifference in a location of the center of the first geometricconfiguration and a location of the center of the second geometricconfiguration.
 18. The method of claim 13, further comprising the stepsof:computing first summations respectively summing intensities of thegenerated first image in an x direction, in a y direction and in adiagonal direction; computing second summations respectively summingintensities of the generated second image in the x direction, in the ydirection and in the diagonal direction; generating the first geometricconfiguration based upon the computed first summations; and generatingthe second geometric configuration based upon the computed secondsummations.
 19. The method of claim 13, further comprising the stepsof:determining another movement of the object in a third of the objectimages based upon a distance between (i)a third geometric configurationhaving a contour different than a contour of the object andcorresponding to the object in the third image and (ii) a fixedreference; and controlling the digital representation based upon thedetermined other movement.
 20. The method of claim 19, wherein:thedistance is a vertical distance and exceeds a threshold; and the digitalrepresentation is controlled to perform a jump sequence based upon thedetermined other movement.
 21. A system for controlling a digitalrepresentation, comprising:an imager configured to generate imageintensity data representing an object in an orientation; and at leastone processor configured (i) to process the generated image intensitydata to generate a geometric configuration, corresponding to thegenerated image intensity data, representing the object, and having acontour different than a contour of the represented object and anorientation corresponding to the orientation of the represented object,and (ii) to generate signals to control a digital representation basedupon the orientation of the geometric configuration.
 22. The system ofclaim 21, wherein the object is a body part.
 23. The system of claim 21,wherein the geometric configuration is a rectangle.
 24. The system ofclaim 21, wherein:the represented object has a position; the generatedgeometric configuration has a position corresponding to the position ofthe represented object; and the at least one processor is furtherconfigured to generate the signals to control the digital representationbased upon the position of the geometric configuration.
 25. The systemof claim 21, wherein:the orientation of the represented object is afirst object orientation, the image data is first image data, and thegeometric configuration is a first geometric configuration and theorientation of the first geometric configuration is a first orientation;the imager is further configured to generate second image datarepresenting the object in a second object orientation; and the at leastone processor is further configured (i) to process the generated secondimage data to generate a second geometric configuration representing theobject, and having a contour different than the contour of the objectrepresented by the second image data and a second orientationcorresponding to the second object orientation of the object, (ii) todetermine a movement of the object from the second object orientation tothe first object orientation based upon the first orientation, and (iii)to generate the signals to control the digital representation inaccordance with the determined movement.
 26. The system of claim 21,wherein said at least one processor is further configured to:compute aspatially weighted average intensity of the generated image data in itsentirety; and generate the geometric configuration based upon thecomputed spatially weighted average.
 27. The system of claim 21,wherein:the object is a hand; the image data represents a circle formedwith a thumb and a finger of the hand; and the at least one processor isconfigured to generate the control signal to thereby trigger an actionresponsive to the thumb contacting the finger to form the circle. 28.The system of claim 21, whereinthe object has a center of mass and thegeometric configuration has a center point; and the center point of thegeometric configuration corresponds to the center of mass of the object.29. The system of claim 21, wherein:the at least one processor isfurther configured to compute summations respectively summingintensities of the generated image data in an x direction, in a ydirection and in a diagonal direction and to generate the geometricconfiguration based upon the computed summations.
 30. The system ofclaim 21, wherein:the represented object has a position; the generatedgeometric configuration has a position corresponding to the position ofthe represented object; the at least one processor is further configuredto determine a distance between the position of the geometricconfiguration and a fixed reference, and to generate the signals tocontrol the digital representation based upon the determined distance.31. The system of claim 30, wherein:the distance is a vertical distanceand exceeds a threshold; and the digital representation is controlled toperform a jump sequence.
 32. The system of claim 21, wherein:the atleast one processor is two processors; and the imager and one of theprocessors form an artificial retina.